The United Nations is calling on the Maldives to hold fresh elections "as soon as possible" after police stopped officials from staging polls on Saturday.

U.N. Secretary-General Ban Ki-moon said he was "deeply concerned by the delay" and urged the country's political leaders and institutions to respect the democratic process.

Former president Mohamed Nasheed won 45 percent of a September vote -- not enough to win the presidency outright. Observers said the election was fair but the nation's supreme court scrapped the results after the third-place candidate alleged irregularities.

On Sunday, Nasheed accused President Waheed Hassan of obstructing the new election and demanded he resign to allow the vote to take place under a caretaker government. A presidential spokesman denied the allegations and said Hassan would not step down.

Further delays risk sending the country into a constitutional crisis; the next president is due to be inaugurated on November 11.

Nasheed was the first democratically elected Maldivian president, but was forced to resign at gunpoint in 2012.